Blasting cap



Patented Dec. 9, I924. I

UNITED STATES PATENT OFFICE.

CLIFFORD A. WOODBUBY, 01? MEDIA, PENNSYLVANIA, ASSIGNOR TO E. I. DU PONT'DE NEMOUBS & COMPANY, OF WILMINGTON, DELAWARE, A QORPORATION OF DELA WARE.

BLASTING CAP.

No Drawing.

To all whom it may concern:

' detonation.

Be it known that I, CLIFFORD .A. WOOD- BURY, a citizen of the United States, and a resident of Media, in the county of Delaware and State of Pennsylvania, have invented acertain new and useful Blasting Cap, of which the following is a specification. I i

This invention relates to blasting caps, and, more particularly to blasting caps of the composition type. Such caps, as usually manufactured, comprise a metallic shell containing a base charge and a primer charge pressedon the top of the base charge. Among the explosives used for the base charge have been, for example, trinitrotoluene, tetranitromethylaniline, tetranitroaniline, and nitrated ivory nut meal. For .the primer charge have been usedprimary detonating compounds such as mercury fulminate, lead azide, cyanurtriazide, and diazodinitrophenol, various oxidizing agents such as potassium chlorate being often mixed with the priming compound. A perforated capsule may be pressed down on the top of the primer charge for the purpose of giving additional confinement to the charge and thereby increasing the elficiency of the The practice of using a base charge of some explosive less expensive than I mercury fulminate, instead of using a charge of fulminate alone, arose as a meas-' ure of economy; by the present invention a portion of the enormous stock of propellent explosives on hand in many countries at the close of the war may be economically utilized in basecharges. I An object of the present invention is to provide a cap having a charge of great efficiency inthe detonation of other explosives, and at the same time to produce an economy in the cost of the explosive materials used in the cap. To this end, and also to improvegen erally-upon caps of the general character indicated, my invention consists in the various matters hereinafter described and claimed.

In brief, my invention comprises the use of .finely ground pyro powder as the base charge, meaning by pyro powder that grade of smokeless powder made from nitrocellulose almost completely soluble in a mixture of two parts by volume of ether to' one part of ethyl alcohol and having a nitrogen content of about-12.60%. Large stocks Application filed February 5, 1924. Serial No; 690,882.

of this powder were left on hand at the close of the recent war, and should be utilized.

It is not, however, itself a detonating agent, that is, a detonation cannot be set up in relatively small quantities of it by the explosion of an adjacent small charge of mercury fulminate. .N ow I have discovered that when such pyro powder is finely ground, it

becomes a satisfactory material for use as a-base charge in a detonator. I have found that to some extent the efficiency of the detonation of the ground pyro powder is dependent on the degree of subdivision. For

example, material so ground that everything passes a 30 mesh screen, and with 35% passing a 100 mesh screen makes a rather weak, low velocity base charge, while material s0 ground that passes a 100 mesh screen makes a very satisfactory base charge. I prefer to use .pyro powder so ground that at least 90% passes a 100 mesh screen. 1 4

In loading a shellI may, for example, press into the cap shell 6 grains of ground pyro powder, Jusing a pressure of 180 to 200 pounds per square inch, and on top of this, -I may press 6 grains of a mixture of 90% mercury fulminate and 10% potassium chlorate with a super-imposed copper ca sule using a pressure of about 160 poun s per square inch. A very eflicient detonator is thus produced.

It will be understood that I do not con-- fine the invention to the weights of material,

the relative proportions of the base and primer charges or: the pressures above stated,

- of which great quantities are now on hand and whose utilization is, therefore, particularly desirable, it will be understood that the invention is not confined to that particular nitrocellulose smoLeless powder.

I claim:

1. A detonator having a charge comprising ground smokeless powder.

2. A detonator having a main charge comprising ground smokeless powder, and a pripass a 100 mesh screen, and a primary detomary detonating compound. nating compound.

3. A detonator having a secondary charge 5. A detonator having a Base charge of co'mprising finely ground smokeless powder, ground pyro powder having a, fineness such and a primary detonating charge of fulmithat all will pass a 30 mesh screen and at nate of mercury. least substantially 90% will pass a 100 mesh 4. A detonator having a base charge comscreen, and a top chargev of fulminate of prising ground pyro powder having a finemercury. ness such that all will pass a mesh screen In testimony whereof I afiix m signature. 10 and substantially between and will CLIFFORD A. WOO BURY. 

